No good, I installed the nvidia-180-kernel-source_185.18.14-0ubuntu1~xup~1~jaunty_amd64.deb, nvidia-180-libvdpau_185.18.14-0ubuntu1~xup~1~jaunty_amd64.deb & nvidia-glx-180_185.18.14-0ubuntu1~xup~1~jaunty_amd64.deb packages, did a reboot and (user) glxinfo says:

dc@dc-master:~$ glxinfo
name of display: :0.0
NVIDIA: could not open the device file /dev/nvidiactl (Permission denied).
display: :0 screen: 0
direct rendering: No (If you want to find out why, try setting LIBGL_DEBUG=verbose)

same here for me as well
I only get direct rendering now if i run something as root using the nvidia driver 185
google earth is zooming as root with direct rendering yes, normal user very very slow. so anyone know how to fix so user gets direct rendering?

Somehow my /dev/nvidiactl (190.42 driver) in karmic has the group www-data. So I added myself to this group and everything seems to work fine. Especially Adobes Flash Player stops flickering after that.

This bug report was filed against an old version of Ubuntu.
Can you confirm whether this is still an issue in natty?

If you don't mind, it would be very helpful if you could update the bug
report in launchpad to 'Fix Released' if it is no longer an issue for
you, or if it is still occurring under natty, please tag the bug 'natty'
so it's easier for us to track.

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.